RT6212C/D
Operation
The RT6212C/D is a synchronous step-down converter
with advanced constant on-time control mode. Using
the ACOT
TM
control mode can reduce the output
capacitance and provide fast transient response. It can
minimize the component size without additional
external compensation network.
Soft-Start (SS)
The RT6212C/D provides an internal soft-start feature
for inrush control. At power up, the internal capacitor is
charged by an internal current source I
SS
to generate a
soft-start ramp voltage as a reference voltage to the
PWM comparator. The device will initiate switching and
the output voltage will smoothly ramp up to its targeted
regulation voltage only after this ramp voltage is
greater than the feedback voltage V
FB
to ensure the
converters have a smooth start-up. The output voltage
starts to rise in 85s from EN rising, and the soft-start
ramp-up time (V
FB
from 0V to 0.8V) is 1ms.
Output Under-Voltage Protection and Hiccup Mode
The RT6212C/D includes output under-voltage
protection (UVP) against over-load or short-circuited
condition by constantly monitoring the feedback
voltage V
FB
. If V
FB
drops below the under-voltage
protection trip threshold (typically 50% of the internal
feedback reference voltage), the UV comparator will go
high to turn off both the internal high-side and low-side
MOSFET switches.
If the output under-voltage condition continues for a
period of time, the RT6212C/D will enter output
under-voltage protection with hiccup mode. During
hiccup mode, the IC will shut down for t
HICCUP_OFF
(3.6ms), and then attempt to recover automatically for
t
HICCUP_ON
(1.2ms). Upon completion of the soft-start
sequence, if the fault condition is removed, the
converter will resume normal operation; otherwise,
such cycle for auto-recovery will be repeated until the
fault condition is cleared. Hiccup mode allows the
circuit to operate safely with low input current and
power dissipation, and then resume normal operation
EN
as soon as the over-load or short-circuit condition is
removed.
Abnormal case
detected (UV)
Resume normal
operation
t
HICCUP_ON
= 1.2ms
t
HICCUP_OFF
= 3.6ms
Fault condition
removed
t
1ms
FB
85μs
1ms
VOUT
LX
UVLO Protection
To protect the chip from operating at insufficient supply
voltage, the UVLO is needed. When the input voltage
of VIN is lower than the UVLO falling threshold voltage,
the device will be lockout.
Thermal Shutdown
When the junction temperature exceeds the OTP
threshold value, the IC will shut down the switching
operation. Once the junction temperature cools down
and is lower than the OTP lower threshold, the
converter will autocratically resume switching.
t
Copyright © 2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6212C/D-01
September 2018
www.richtek.com
3
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
